This invention relates to polycrystalline ceramic composite lasers. Ikesue et al. disclose xe2x80x9cFabrication . . . of Polycrystalline Nd:YAG Ceramics for . . . Lasersxe2x80x9d in J. Am. Ceram. Soc., vol. 78(4), p. 1033-40 (1995). Greskovich et al. disclose in U.S. Pat. No. 3897358 a method of pressing and sintering polycrystalline laser material. Taira, Ikesue and Yoshida have disclosed efficient laser operation of Nd:YAG polycrystalline ceramic microchips in xe2x80x9cPerformance . . . Nd-doped YAG Ceramic Microchip Lasersxe2x80x9d, in CLEO""99 Technical Digest, p. 136 (May /1999). It is taught that this new polycrystalline ceramic form allows higher doping, which provides 10 times higher absorption of pump energy, and it is reported that the maximum output power is four times higher than that of Nd:YAG single crystal.
However, due to higher absorption coefficient of these highly doped polycrystalline ceramics, experimental laser specimens of the prior art generate excessive heat that degrades the various coatings required to form optical laser cavities. This has resulted in the premature failure of the laser cavity. Therefore, there is a need to produce a polycrystalline laser that can efficiently dissipate the additional heat generated therein during laser operation to allow long term, reliable laser operation.
An object of the present invention is to provide a polycrystalline laser having a means of dissipating heat efficiently, so that the optical coatings maintain their integrity during long-term laser use. Another object of the present invention is to provide various novel, unique embodiments of end-pumped and side-pumped polycrystalline lasers which can survive long term use. Another object of the present invention is to provide a polycrystalline laser that accomplishes the above objects at low energy consumption and low manufacturing cost.
These and other objects of the present invention are achieved in the present invention by a doped polycrystalline laser ceramic being contiguous with an undoped or pure, polycrystalline ceramic. The pure, undoped ceramic portion functions to efficiently dissipate the heat generated within the doped laser ceramic during laser operation. Low energy consumption is provided by the higher absorption of the doped polycrystalline, because of the higher allowed dopant concentrations. Low manufacturing cost is achieved by creating the laser gain material and the heat sink out of the same ceramic, thus minimizing the number of different materials that must be assembled.